Francisella tularensis, the aetiological agent of tularemia, is one of the most infectious bacterial pathogens currently known and a NIAID category A priority pathogen because of its potential for use as a biological weapon. Unlike many other intracellular pathogenes Francisella encodes relatively few transcription regulators. Although some of these transcription regulators are known to play critical roles in the control of virulence genes required for intracellular survival, for the majority of them it is not known whether they play a role in the control of virulence gene expression. Here we propose to use chromatin immunoprecipitation (ChIP) coupled with fully tiled high density DNA microarrays (ChIP-on-chip) to identify the regulatory targets (i.e. genomic locations) for every predicted transcription regulator in Francisella. In this manner we will be able to (i) understand how certain regulators that are known to play an important role in pathogenesis achieve control over the genes they regulate, (ii) comprehensively determine which subset of the transcription regulators in Francisella are involved in controlling the expression of known virulence genes, and (iii) reveal how any putative connections between the regulatory networks governing virulence gene expression in Francisella allow for the coordinate expression of genes required for intracellular growth. By determining the genomic locations of every transcription factor in Francisella we will be able to define all of the virulence regulatory networks operating in the cell at the level of transcription, and thus identify possible points of therapeutic intervention. PUBLIC HEALTH RELEVANCE: F. tularensis, the causative agent of tularemia, is a potential bioweapon and a NIAID category A priority pathogen. The proposed experiments are expected to reveal how an important intracellular pathogen regulates the expression of genes that are required to cause disease. Our work has implications for the development of therapeutics for the treatment of tularemia.